Ten years ago, Alastair Campbell spoke on behalf of the whole nation, not just Tony Blair, when he said "We don't do God". But the very fact Campbell needed to spell this out was a sign that, post 9/11, things were changing. In 2006, Richard Dawkins published The God Delusion and everyone has been talking God ever since.

For a while it was at least invigorating. But the most vocal atheists and the believers who take their bait appear ever more like a long-married couple who prefer the familiarity of their dysfunctional relationship to the emptiness that lies beyond an amicable divorce. They trade the same old niggles and complaints with no hope or expectation of mutual understanding.

AC Grayling has been one of the leading atheist protagonists. He writes as one confident that he holds all the best cards, and he has already played them with style in his anti-religion book Against All Gods and his pro-humanist What is Good? and The Choice of Hercules. For The God Argument he has shuffled the pack once more and brought both the negative and positive sides of his position together in one volume.

Grayling's case is most powerful against those who believe, literally, that holy texts convey the word of God, who is a real, personal being who cares for, rewards and punishes us. For a sensible philosopher like Grayling, this is all-too obviously ridiculous, and by the second chapter, he is already unable to resist making the inevitable comparisons with tooth fairies and Father Christmas.

Most intelligent defenders of religion don't buy this nonsense either and protest that this misses the point. But Grayling is not attacking a straw man. Even the most intellectually sophisticated Christians, for example, usually draw the line at the empty tomb, believing that if Jesus did not really rise from the dead, then their faith is empty. It is simply disingenuous for them to complain about Grayling's excessive literalness while their entire faith quietly rests on a literal belief in Christ's resurrection.

Nonetheless, there is much more to faith than a stone-age metaphysics of divine beings and miracles. Grayling, however, dismisses all the rest as the mere residue of an outdated worldview or the obfuscation of confused minds. For him, the matter is simple: all religion is built on supernatural beliefs and "when one rejects the premise of a set of views, it is a waste of one's time to address what is built on those premises". As a result, he simply refuses to engage with the most interesting aspect of the God debate: what, if anything, remains of truth and value in religion if you accept its stories as myths?

The second half of the book builds a positive case for humanism, which is in broad terms simply the reasonable and sensible working through of the idea that "our ethics must be drawn from, and responsive to, the nature and circumstances of human experience". However, as an unapologetic champion of humanism, Grayling skirts over its more problematic aspects. He rightly stresses the importance of reason and autonomy, for example, but doesn't deal with the serious worries that we are nowhere near as free or rational as traditional humanists have believed. Similarly, he presents a vision of the good life without taking seriously enough the possibility that we could equally despair at the meaninglessness of it all.

The God Argument sums up the mainstream humanist position well, but I can't see it taking the debate forward. Perhaps that would be a foolish hope. The public debate Dawkins started seems to have done as much to make the participants feel validated as it has to change their opinions. The God argument remains unwinnable.